# Test: Arithmetic Series - Ambitious

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Question 1:   What is the common difference in the following arithmetic series: $2.5,6.4,10.3,...$?
$2.56$
$7.8$
$3.9$
$3.2$
Question 2:   Which of the following sequences is an arithmetic series?
$0.125,0.250,0.38,0.515,0.655$
$17.5,15,12.5,10,7.5$
$1,2,3,5,8,13$
$16,8,4,2,1$
Question 3:   What is the $25$th term in the following arithmetic series: $1,4,7,10...$?
$72$
$75$
$74$
$73$
Question 4:   What is the $31$st term in the following arithmetic series: $45,42.5,40...$?
$-31.75$
$-30$
$110$
$-27.25$
Question 5:   What is the sum of the first $21$ terms in the following arithmetic series: $3,5,7,9$?
${S}_{21}=512$
${S}_{21}=483$
${S}_{21}=241$
${S}_{21}=368$
Question 6:   What is the sum of the first $18$ terms in the following series: $21,17,13$?
${S}_{18}=-212$
${S}_{18}=-256$
${S}_{18}=-198$
${S}_{18}=-234$
Question 7:   How many terms in the following arithmetic series $5,9,13,...$ must be taken if the sum is $702$?
$14$
$21$
$18$
$23$
Question 8:   How many terms in the following arithmetic series $0.25,0.75...,$ must be taken if the sum is $156.25$?
$45$
$30$
$60$
$25$
Question 9:   If the $7$th term is $15$ and the $20$th term is $41$, find the series
$-3,0,3$
$3,5,7,9$
$2,4,6$
$9,10,11$
Question 10:   If the $5$th term is $10$ and the $11$th term is $-14$, find the sum of the first $20$ terms
${S}_{20}=-240$
${S}_{20}=-160$
${S}_{20}=-120$
${S}_{20}=-200$